Adaptation of the Oxygen Affinity of Haemoglobin in Acute Hypoxia*,**

Summary. When the adaptation of the oxygen affinity of haemoglobin (Hb) to acute hypoxia is tested in healthy volunteers with and without Dipyridamole1 (D), the Bohr‐effect is shown to play the dominant role for the position of the oxygen dissociation curve (ODC). If the Bohr‐effect is eliminated by calculating a pH corrected P50, a shift to the right is observed after only 2 hours of continued hypoxia. This decrease of the O2‐affinity of Hb correlates with an increase in red cell 2, 3‐DiphosphogIycerate (DPG). Under D.‐medication the 2, 3‐DPG levels are significantly higher than the controls. The 2% increase of O2‐availability induced by D. however is fully reversed by the Bohr effect. To raise the O2 supply at the tissue level in acute hypoxia, the human organism prefers an increase in O2‐binding and ‐transport to a decrease in the O2‐affinity of Hb. The continued respiratory alkalosis raises the 2, 3‐DPG level thus gradually compensating for the primary increase in the oxygen affinity of haemoglobin.